Conventionally, a surface (processing surface) of a thin substrate (object to be polished) such as materials for semiconductor devices, electronic components and the like, in particular, a Si substrate (silicon wafer), a GaAs (gallium arsenide) substrate, glass, and substrates for a hard disk drive and an LCD (liquid crystal display) is required to be flat. Accordingly, chemical mechanical polishing is performed thereon using a polishing pad along with polishing slurry. Meanwhile, some materials which can be applied to forthcoming power devices and the like, such as sapphire, SiC, GaN and diamond, are known as hard-to-process materials, which are difficult to polish.
To date, in an effort to develop a novel polishing technique, materials, structures and polishing conditions for the polishing pad and the polishing slurry have been studied with reference to so-called Prestonian's empirical rule. Simply to say, Prestonian's empirical rule is a rule empirically indicating that the removal rate (polishing rate) of the object to be polished is proportional to a relative speed between the polishing pad and the object to be polished (hereinafter referred to simply as “relative speed”), a pressing force between these (hereinafter referred to simply as “polishing pressure”), and a polishing time. It is known, however, that even an increase in the relative speed and the polishing pressure based on Prestonian's empirical rule is not sufficient for efficiently polishing the object to be polished (hereinafter also referred to as “workpiece”), in particular, the hard-to-process material in a short time because of factors such as limitation in capability of the polishing apparatus.
Therefore, slurry which exhibits non-Prestonian behavior has been studied as the polishing slurry. For example, Patent Document 1, which is intended to provide a method for manufacturing polishing slurry in which dispersion stability is improved and which exhibits non-Prestonian polishing characteristics, proposes a method for manufacturing polishing slurry, the method including: (a) a step of dispersing abrasive particles and a dispersing agent of anionic polymer acid in water; and (b) a step of adding, to the generated dispersion, an alkaline substance of an amount of 0.1 to 8 parts by weight on the basis of 100 parts by weight of abrasive particles as a reference.